Daun gained field experience during Austrian operations in Sicily (17181719), in Italy and on the Rhine (1734–35), against Turkey (1737–39), and during the War of the Austrian Succession (1740–48). He then began to reorganize the Austrian army, increasing troop strength, initiating better discipline and training, and founding a cadet school. As a result, Austria’s army became a far more formidable opponent to Frederick the Great than the Prussian monarch had expected.

During the Seven Years’ War, Daun, though often criticized for his overcautious strategy, nevertheless defeated Frederick at Kolín (June 1757) and replaced Charles of Lorraine as supreme commander after the Austrian defeat at Leuthen (December 1757). After other victories over the Prussians at Hochkirch (1758) and Maxen (1759), he was finally defeated at Torgau (1760). In 1762 he became president of the Imperial War Council (Hofkriegsrat), where he once again championed various army reforms, among them the centralization of military authority in the war council and the improvement of the cadet academy.